Semiconductor light emitting device and method for manufacturing same

ABSTRACT

According to one embodiment, a semiconductor light emitting device includes a semiconductor layer, a first electrode, a second electrode, an insulating film, a first interconnection, a second interconnection, a first metal pillar, a second metal pillar, a resin, and a fluorescent layer. The semiconductor layer has a first major surface, a second major surface formed on an opposite side to the first major surface, and a light emitting layer. The first electrode and the second electrode are provided on the second major surface of the semiconductor layer. The fluorescent layer faces to the first major surface of the semiconductor layer and includes a plurality of kinds of fluorescent materials having different peak wavelengths of emission light.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2010-069716, filed on Mar. 25, 2010; theentire contents of which are incorporated herein by reference.

BACKGROUND

Light emitting devices capable of emitting visible and white light areexpanding their applications to, for instance, illumination devices,display devices, and backlight sources for image display devices.

In these applications, there is a growing demand for downsizing. In thiscontext, downsizing of electronic devices has been facilitated by an SMD(surface-mounted device) light emitting device in which a light emittingelement chip is bonded onto a lead frame and molded with resin.

To replace fluorescent lamps and incandescent bulbs by illuminationdevices based on semiconductor light emitting devices with low powerloss, it is necessary to enhance mass productivity and reduce cost.

An example technique for further downsizing is disclosed. In thisexample technique, a light emitting element chip is flip-chip connectedto an interconnect layer provided on a transparent substrate so as to beexternally driven via a columnar electrode and a ball. On thetransparent substrate, the light emitting element chip and the columnarelectrode are covered with a sealant.

However, this example needs the interconnect layer and the columnarelectrode for bonding the light emitting element chip onto thetransparent substrate with high positional accuracy, and it isinsufficient to meet the requirements for downsizing and massproductivity.

Furthermore, in a fluorescent-conversion white LED (light emittingdiode), wavelength conversion of excitation light by the fluorescentmaterial cannot avoid Stokes loss in which the energy difference betweenthe excitation light and the fluorescent-emitted light is lost as heat.Thus, efficiency improvement by controlling the fluorescent material isdesired.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a semiconductor lightemitting device of an embodiment;

FIG. 2 is an enlarged sectional view of a relevant part in FIG. 1,

FIG. 3 is a schematic plain view of a method for manufacturing asemiconductor light emitting device of the embodiment in wafer state;

FIGS. 4A to 7B are schematic cross-sectional views of a method formanufacturing a semiconductor light emitting device of the embodiment;and

FIG. 8 is a schematic cross-sectional view of a semiconductor lightemitting device of another embodiment.

DETAILED DESCRIPTION

According to one embodiment, a semiconductor light emitting deviceincludes a semiconductor layer, a first electrode, a second electrode,an insulating film, a first interconnection, a second interconnection, afirst metal pillar, a second metal pillar, a resin, and a fluorescentlayer. The semiconductor layer has a first major surface, a second majorsurface formed on an opposite side to the first major surface, and alight emitting layer. The first electrode is provided on the secondmajor surface of the semiconductor layer. The second electrode isprovided on the second major surface of the semiconductor layer. Theinsulating film is provided on a side of the second major surface of thesemiconductor layer and includes a first opening reaching the firstelectrode and a second opening reaching the second electrode. The firstinterconnection is provided on a surface of the insulating film on theopposite side to the semiconductor layer and in the first opening and isconnected to the first electrode. The second interconnection is providedon a surface of the insulating film on the opposite side to thesemiconductor layer and in the second opening and is connected to thesecond electrode. The first metal pillar is provided on a surface of thefirst interconnection on an opposite side to the first electrode. Thesecond metal pillar is provided on a surface of the secondinterconnection on an opposite side to the second electrode. The resincovers a periphery of the first metal pillar and a periphery of thesecond metal pillar. The fluorescent layer faces to the first majorsurface of the semiconductor layer and includes a plurality of kinds offluorescent materials having different peak wavelengths of emissionlight.

Embodiments will now be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of a semiconductor lightemitting device of an embodiment.

The semiconductor light emitting device of this embodiment includes asemiconductor layer 5, a package structure section includinginterconnections, sealing resin and the like, and a fluorescent layer27, which are formed collectively in wafer state. The semiconductorlayer 5 includes a first semiconductor layer 11 and a secondsemiconductor layer 12. The first semiconductor layer 11 isillustratively an n-type GaN layer and functions as a lateral currentpath. However, the conductivity type of the first semiconductor layer 11is not limited to n-type, but may be p-type.

Light is extracted to the outside mainly from the first major surface 11a of the first semiconductor layer 11. The second semiconductor layer 12is provided on the second major surface 11 b of the first semiconductorlayer 11 on the opposite side to the first major surface 11 a.

The second semiconductor layer 12 has a stacked structure of a pluralityof semiconductor layers including a light emitting layer (active layer).FIG. 2 shows an example of this structure. It is noted that FIG. 2 isvertically inverted from FIG. 1.

An n-type GaN layer 31 is provided on the second major surface 11 b ofthe first semiconductor layer 11. A light emitting layer 33 is providedon the GaN layer 31. The light emitting layer 33 illustratively has amultiple quantum well structure including InGaN. A p-type GaN layer 34is provided on the light emitting layer 33.

As shown in FIG. 1, a protrusion and a depression are provided on thesecond major surface 11 b side of the first semiconductor layer 11. Thesecond semiconductor layer 12 is provided on the surface of theprotrusion. Hence, the protrusion includes the stacked structure of thefirst semiconductor layer 11 and the second semiconductor layer 12.

The bottom surface of the depression is the second major surface 11 b ofthe first semiconductor layer 11, and an n-side electrode 14 is providedas a first electrode on the second major surface 11 b of the depression.

A p-side electrode 15 is provided as a second electrode on the oppositesurface of the second semiconductor layer 12 with respect to the surfacein contact with the first semiconductor layer 11.

The second major surface 11 b of the first semiconductor layer 11 iscovered with an insulating film 13 such as silicon oxide film. Then-side electrode 14 and the p-side electrode 15 are exposed from theinsulating film 13. The n-side electrode 14 and the p-side electrode 15are insulated by the insulating film 13 and serve as electrodeselectrically independent of each other. Furthermore, the insulating film13 also covers the side surface of the protrusion including the secondsemiconductor layer 12.

An insulating film 16 is provided on the second major surface 11 b sideso as to cover the insulating film 13, part of the n-side electrode 14,and part of the p-side electrode 15. The insulating film 16 isillustratively made of silicon oxide film or resin.

The surface of the insulating film 16 on the opposite side to the firstsemiconductor layer 11 and the second semiconductor layer 12 isplanarized, and an n-side interconnection 17 as a first interconnectionand a p-side interconnection 18 as a second interconnection are providedon that surface.

The n-side interconnection 17 is provided also in the opening 16 aformed in the insulating film 16 and reaching the n-side electrode 14and is electrically connected to the n-side electrode 14. The p-sideinterconnection 18 is provided also in the opening 16 b formed in theinsulating film 16 and reaching the p-side electrode 15 and iselectrically connected to the p-side electrode 15.

For instance, the n-side interconnection 17 and the p-sideinterconnection 18 are simultaneously formed by a plating process inwhich a seed metal formed on the surface of the insulating film 16including the inner wall surfaces of the openings 16 a and 16 b is usedas a current path.

The n-side electrode 14, the p-side electrode 15, the n-sideinterconnection 17, and the p-side interconnection 18 are all providedon the second major surface 11 b side of the first semiconductor layer11 and constitute a interconnect layer for supplying a current to thelight emitting layer.

An n-side metal pillar 19 is provided as a first metal pillar on thesurface of the n-side interconnection 17 on the opposite side to then-side electrode 14. A p-side metal pillar 20 is provided as a secondmetal pillar on the surface of the p-side interconnection 18 on theopposite side to the p-side electrode 15. The periphery of the n-sidemetal pillar 19, the periphery of the p-side metal pillar 20, the n-sideinterconnection 17, and the p-side interconnection 18 are covered with aresin 26. Furthermore, the resin 26 covers also the side surface 11 c ofthe first semiconductor layer 11. Thus, the side surface 11 c of thefirst semiconductor layer 11 is protected by the resin 26.

A contact area between the n-side interconnection 17 and the n-sidemetal pillar 19 is larger than a contact area between the n-sideinterconnection 17 and the n-side electrode 14. A contact area betweenthe p-side interconnection 18 and the p-side metal pillar 20 is largerthan a contact area between the p-side interconnection 18 and the p-sideelectrode 15.

The first semiconductor layer 11 is electrically connected to the n-sidemetal pillar 19 via the n-side electrode 14 and the n-sideinterconnection 17. The second semiconductor layer 12 is electricallyconnected to the p-side metal pillar 20 via the p-side electrode 15 andthe p-side interconnection 18. External terminals 25 such as solderballs and metal bumps are provided on the lower end surfaces of then-side metal pillar 19 and the p-side metal pillar 20 exposed from theresin 26, and the semiconductor light emitting device can beelectrically connected to external circuits via the external terminals25.

The thickness of the n-side metal pillar 19 (a thickness in a verticaldirection in FIG. 1) is thicker than the thickness of the stacked bodyincluding the semiconductor layer 5, the n-side electrode 14, the p-sideelectrode 15, the insulating films 13 and 16, the n-side interconnection17, and the p-side interconnection 18. Likewise, the thickness of thep-side metal pillar 20 is also thicker than the thickness of theaforementioned stacked body. The aspect ratio (the ratio of thickness toplanar size) of each of the metal pillars 19 and 20 is not limited toone or more, but the ratio may be less than one. That is, the thicknessof the metal pillars 19 and 20 may be smaller than its planar size.

In the structure of this embodiment, even if the semiconductor layer 5is thin, its mechanical strength can be maintained by thickening then-side metal pillar 19, the p-side metal pillar 20, and the resin 26.Furthermore, the n-side metal pillar 19 and the p-side metal pillar 20can absorb and relax the stress applied to the semiconductor layer 5 viathe external terminals 25 when the device is mounted on a circuit boardor the like. Preferably, the resin 26 serving to reinforce the n-sidemetal pillar 19 and the p-side metal pillar 20 has a thermal expansioncoefficient, which is equal or close to that of the circuit board andthe like. Examples of such a resin 26 include epoxy resin, siliconeresin, and fluororesin.

The n-side interconnection 17, the p-side interconnection 18, the n-sidemetal pillar 19, and the p-side metal pillar 20 can be made of such amaterial as copper, gold, nickel, and silver. Among them, it is morepreferable to use copper, which has good thermal conductivity, highmigration resistance, and superior contact with insulating films.

The fluorescent layer 27 is provided on the first major surface 11 a ofthe first semiconductor layer 11. The fluorescent layer 27 is providedwith a generally uniform thickness in the plane direction of the firstmajor surface 11 a. Light emitted from the light emitting layer passesmainly the first semiconductor layer 11, the first major surface 11 aand the fluorescent layer 27, and is emitted to the outside.

The fluorescent layer 27 can absorb the light (excitation light) fromthe light emitting layer and emit wavelength-converted light. Thus, itis possible to emit mixed light of the light from the light emittinglayer and the wavelength-converted light of the fluorescent layer 27.

The fluorescent layer 27 has a structure in which a plurality of kindsof fluorescent materials are dispersed in a transparent resin. Thetransparent resin is transmissive to light emitted by the light emittinglayer and the fluorescent materials and is illustratively siliconeresin.

The plurality of kinds of fluorescent materials include ones, which areexcited by light from the light emitting layer and emit light atdifferent peak wavelengths. Relatively, the fluorescent materials havinga longer peak wavelength are provided nearer to the first major surface.The fluorescent materials having different peak wavelengths are layeredalong the thickness of the fluorescent layer 27.

The fluorescent layer 27 includes a first fluorescent layer 27 aprovided on the first major surface 11 a and containing a firstfluorescent material and a second fluorescent layer 27 b provided on thefirst fluorescent layer 27 a. The second fluorescent layer 27 b containsa second fluorescent material having a shorter peak wavelength ofemission light than the first fluorescent material. Here, thefluorescent layer 27 may have a stacked structure of three or morelayers.

By allowing the fluorescent layer 27 to contain a plurality of kinds offluorescent materials having different peak wavelengths of emissionlight, high color rendering property (the property of a light sourcedetermining the apparent color of an object illuminated thereby) can beobtained. Furthermore, by using a light emitting layer emitting bluelight and using as the fluorescent materials a red fluorescent materialemitting red light and a green fluorescent material emitting greenlight, a white color or lamp color with high color rendering propertycan be obtained as mixture of the blue light, red light, and greenlight.

In this layered structure, the first fluorescent layer 27 a containing ared fluorescent material as a first fluorescent material is provided onthe first major surface 11 a side from which light from the lightemitting layer is emitted, and the second fluorescent layer 27 bcontaining a green fluorescent material as a second fluorescent materialhaving a shorter light emission peak wavelength is provided thereon.Thus, the emission light of the fluorescent material is not consumed toexcite other kinds of fluorescent materials, and the efficiency decreasecan be suppressed. Consequently, highly efficient light emissioncharacteristics can be achieved.

Emission light with a desired color can be obtained by adjusting thedensity of the green fluorescent material and red fluorescent materialand the thickness of the fluorescent layers containing them.

As the fluorescent materials, by using fluorescent materials in whichSiAlON compounds as illustrated below are doped with emission centerelements, the temperature characteristics of wavelength conversionefficiency is improved, and the efficiency in the high current densityregion can be further improved. Furthermore, the green SiAlONfluorescent material and red SiAlON fluorescent material are excitedwith high efficiency by blue light. Hence, by combination with a lightemitting layer emitting blue light, a highly efficient light emittingdevice with various shades can be obtained.

As compared with the combination of a yellow fluorescent material withblue excitation light, the combination of a red SiAlON fluorescentmaterial and a green SiAlON fluorescent material with blue excitationlight is more preferable to obtain a white color with higher colorrending property and, it also suppresses degradation at hightemperatures.

Furthermore, the red SiAlON fluorescent material has a broad lightemission spectrum, allowing excitation with high efficiency across awide excitation bandwidth from ultraviolet to blue light, and issuitable particularly for a white LED.

For instance, the first fluorescent layer 27 a contains, as a firstfluorescent material (red fluorescent material), a fluorescent materialwhich exhibits a light emission peak at a wavelength ranging from 580 to700 nm when excited by light with a wavelength of 250 to 500 nm andsatisfies the following formula (1).

(M_(1-x)R_(x))_(a1)AlSi_(b1)O_(c1)N_(d1)  (1)

In the above formula (1), M is at least one metallic element except Siand Al and is preferably at least one of Ca and Sr in particular. R isan emission center element and is preferably Eu in particular.

For instance, M is at least one selected from the group consisting ofMg, Ca, Sr, Ba, Y, Gd, La, Lu, Sc, Li, Na, K, B, Ga, In, and Ge. R is atleast one selected from the group consisting of Eu, Ce, Mn, Tb, Yb, Dy,Sm, Tm, Pr, Nd, Pm, Ho, Er, Gd, Cr, Sn, Cu, Zn, Ga, Ge, As, Ag, Cd, In,Sb, Au, Hg, TI, Pb, Bi, and Fe. Here, x, a1, b1, c1, and d1 satisfy therelations 0<x≦1, 0.6<a1<0.95, 2<b1<3.9, 0.25<c1<0.45, and 4<d1<5.7.

Use of SiAlON fluorescent materials represented by the above compositionformula (1) can improve the temperature characteristics of wavelengthconversion efficiency and further increase the efficiency in the highcurrent density region.

Furthermore, for instance, the second fluorescent layer 27 b contains,as a second fluorescent material (green fluorescent material), afluorescent material which exhibits a light emission peak at awavelength ranging from 490 to 580 nm when excited by light with awavelength of 250 to 500 nm and satisfies the following formula (2).

(M_(1-x)R_(x))_(a2)AlSi_(b2)O_(c2)N_(d2)  (2)

In the above formula (2), M is at least one metallic element except Siand Al and is preferably at least one of Ca and Sr in particular. R isan emission center element and is preferably Eu in particular.

For instance, M is at least one selected from the group consisting ofMg, Ca, Sr, Ba, Y, Gd, La, Lu, Sc, Li, Na, K, B, Ga, In, and Ge. R is atleast one selected from the group consisting of Eu, Ce, Mn, Tb, Yb, Dy,Sm, Tm, Pr, Nd, Pm, Ho, Er, Gd, Cr, Sn, Cu, Zn, Ga, Ge, As, Ag, Cd, In,Sb, Au, Hg, TI, Pb, Bi, and Fe. Here, x, a2, b2, c2, and d2 satisfy therelations 0<x≦1, 0.93<a2<1.3, 4.0<b2<5.8, 0.6<c2<1, and 6<d2<11.

Use of SiAlON fluorescent materials represented by the above compositionformula (2) can improve the temperature characteristics of wavelengthconversion efficiency and further increase the efficiency in the highcurrent density region.

Alternatively, for instance, the second fluorescent layer 27 b contains,as a second fluorescent material (green fluorescent material), afluorescent material which exhibits a light emission peak at awavelength ranging from 490 to 580 nm when excited by light with awavelength of 250 to 500 nm and satisfies the following formula (3).

(M_(1-x)R_(x))_(a2)AlSi_(b2)O_(c2)N_(d2)  (3)

In the Above General Formula (3), M is at Least One metallic elementexcept Si and Al and is preferably at least one of Ca and Sr inparticular. R is an emission center element and is preferably Eu inparticular.

For instance, M is at least one selected from the group consisting ofMg, Ca, Sr, Ba, Y, Gd, La, Lu, Sc, Li, Na, K, B, Ga, In, and Ge. R is atleast one selected from the group consisting of Eu, Ce, Mn, Tb, Yb, Dy,Sm, Tm, Pr, Nd, Pm, Ho, Er, Gd, Cr, Sn, Cu, Zn, Ga, Ge, As, Ag, Cd, In,Sb, Au, Hg, TI, Pb, Bi, and Fe. Here, x, a2, b2, c2, and d2 satisfy therelations 0<x≦1, 0.94<a2<1.1, 4.1<b2<4.7, 0.7<c2<0.85, and 7<d2<9.

Use of SiAlON fluorescent materials represented by the above compositionformula (3) can improve the temperature characteristics of wavelengthconversion efficiency and further increase the efficiency in the highcurrent density region.

By using the fluorescent materials represented by the above compositionformulas, thermal degradation can be suppressed.

Furthermore, even higher color rending property can be achieved byfurther adding a yellow fluorescent material to the aforementioned redfluorescent material and green fluorescent material. The yellowfluorescent material can illustratively be a silicate fluorescentmaterial such as (Sr,Ca,Ba)₂SiO₄:Eu.

It is noted that the red fluorescent material may illustratively be anitride fluorescent material such as CaAISiN₃:Eu. Furthermore, the greenfluorescent material may illustratively be a halophosphate fluorescentmaterial such as (Ba,Ca,Mg)₁₀(PO₄)₆.Cl₂:Eu.

Furthermore, the plurality of kinds of fluorescent materials may includea blue fluorescent material. The blue fluorescent material canillustratively be an oxide fluorescent material such as BaMgAl₁₀O₁₇:Eu.

Next, a method for manufacturing a semiconductor light emitting deviceof this embodiment is described with reference to FIGS. 3, and 4A to 7B.

First, as shown in FIG. 4A, a first semiconductor layer 11 is formed onthe major surface of a substrate 10. The surface of the firstsemiconductor layer 11 on the substrate 10 side corresponds to the firstmajor surface 11 a. Next, a second semiconductor layer 12 is formed onthe second major surface 11 b of the substrate 10 on the opposite sideto the first major surface 11 a. For instance, in the case where thelight emitting layer is made of a nitride semiconductor, the stackedbody of the first semiconductor layer 11 and the second semiconductorlayer 12 can be grown as a crystal on a sapphire substrate.

Next, for instance, an RIE (reactive ion etching) process using aresist, not shown, is used to selectively remove part of the secondsemiconductor layer 12 and the first semiconductor layer 11. Thus, asshown in FIG. 4B, a depression and a protrusion are formed on the secondmajor surface 11 b side of the first semiconductor layer 11. The portionfrom which part of the second semiconductor layer 12 and the firstsemiconductor layer 11 are removed constitutes the depression, and theportion where the second semiconductor layer 12 including the lightemitting layer is left constitutes the protrusion. The second majorsurface 11 b of the first semiconductor layer 11 is exposed to thebottom of the depression.

Next, as shown in FIG. 4C, the entire surface of the second majorsurface 11 b of the first semiconductor layer 11 and the secondsemiconductor layer 12 are covered with an insulating film 13. Theinsulating film 13 is formed illustratively by a CVD (chemical vapordeposition) process.

Next, openings are selectively formed in the insulating film 13. Asshown in FIG. 5A, a p-side electrode 15 is formed on the secondsemiconductor layer 12 of the protrusion, and an n-side electrode 14 isformed on the second major surface 11 b of the first semiconductor layer11 in the depression.

Furthermore, a trench 8 piercing the insulating film 13 and the firstsemiconductor layer 11 and reaching the substrate 10 is formed. Thetrench 8 separates the first semiconductor layer 11 into a plurality onthe substrate 10. The trench 8 is formed illustratively like a latticein the wafer surface as shown in FIG. 3. Thereby, a plurality of chips(semiconductor layers) 5 surrounded by the trench 8 are formed.

Next, as shown in FIG. 5B, an insulating film 16 covering the n-sideelectrode 14, the p-side electrode 15, and the insulating film 13 isformed. The insulating film 16 is buried in the trench 8.

After the insulating film 16 is formed, as shown in FIG. 5C, an opening16 a reaching the n-side electrode 14 and an opening 16 b reaching thep-side electrode 15 are formed in the insulating film 16 illustrativelyby using a hydrofluoric acid solution. The insulating film 16 in thetrench 8 is also removed.

Next, a seed metal, not shown, is formed on the upper surface of theinsulating film 16 and the inner wall (side surfaces and bottomsurfaces) of the openings 16 a and 16 b, and a plating resist, notshown, is further formed. Then, Cu plating is performed using the seedmetal as a current path. The seed metal illustratively includes Cu.Furthermore, the plating resist, not shown, is provided in the trench 8.

Thus, as shown in FIG. 6A, an n-side interconnection 17 and a p-sideinterconnection 18 are selectively formed on the upper surface (thesurface on the opposite side to the first semiconductor layer 11 and thesecond semiconductor layer 12) of the insulating film 16. The n-sideinterconnection 17 is formed also in the opening 16 a and connected tothe n-side electrode 14. The p-side interconnection 18 is formed also inthe opening 16 b and connected to the p-side electrode 15.

Next, the plating resist used for the plating of the n-sideinterconnection 17 and the p-side interconnection 18 is removed withchemicals. Then, another plating resist for forming metal pillars isformed, and electrolytic plating is performed using the aforementionedseed metal as a current path. Also at this time, the plating resist isprovided in the trench 8. Thus, as shown in FIG. 6B, an n-side metalpillar 19 is formed on the n-side interconnection 17, and a p-side metalpillar 20 is formed on the p-side interconnection 18.

Subsequently, the plating resist for forming metal pillars is removedwith chemicals, and furthermore the exposed portion of the seed metal isremoved. This breaks the electrical connection between the n-sideinterconnection 17 and the p-side interconnection 18 via the seed metal.

Next, as shown in FIG. 7A, the n-side interconnection 17, the p-sideinterconnection 18, the n-side metal pillar 19, the p-side metal pillar20, and the insulating film 16 are covered with a resin 26. Furthermore,at this time, part of the resin 26 is buried also in the trench 8.

Subsequently, the surface of the resin 26 is ground to expose the endsurfaces of the n-side metal pillar 19 and the p-side metal pillar 20.Then, external terminals 25 (FIG. 1) such as solder balls and metalbumps are provided on the exposed surfaces.

Next, as shown in FIG. 7B, the substrate 10 is removed. It is noted thatFIG. 7B is vertically inverted from FIG. 7A.

The substrate 10 is removed from the first semiconductor layer 11illustratively by a laser lift-off process. Specifically, laser light isapplied toward the first semiconductor layer 11 from the rear surfaceside of the substrate 10, which is the surface opposite to its majorsurface on which the first semiconductor layer 11 is formed. The laserlight has a wavelength to which the substrate 10 is transmissive andwhich falls in an absorption region of the first semiconductor layer 11.

When the laser light reaches the interface between the substrate 10 andthe first semiconductor layer 11, the first semiconductor layer 11 nearthe interface is decomposed by absorbing the energy of the laser light.For instance, in the case where the first semiconductor layer 11 is madeof GaN, it is decomposed into Ga and nitrogen gas. This decompositionreaction forms a small gap between the substrate 10 and the firstsemiconductor layer 11 and separates the substrate 10 from the firstsemiconductor layer 11. Irradiation with laser light is performedmultiple times on predefined regions throughout the wafer to remove thesubstrate 10.

After the substrate 10 is removed, as shown in FIG. 1, a fluorescentlayer 27 is formed on the first major surface 11 a of the firstsemiconductor layer 11.

For instance, a paste-like transparent resin in which a firstfluorescent material is dispersed is supplied onto the first majorsurface 11 a by a printing process, and then the transparent resin iscured. Thus, a first fluorescent layer 27 a is formed on the first majorsurface 11 a. Subsequently, a paste-like transparent resin in which asecond fluorescent material is dispersed is supplied onto the firstfluorescent layer 27 a by a printing process, and then the transparentresin is cured. Thus, a second fluorescent layer 27 b is formed on thefirst fluorescent layer 27 a. That is, a fluorescent layer 27 with astructure of two layers having different light emission peak wavelengthsis obtained.

When the fluorescent layer 27 is formed, as shown in FIG. 7B, becausethe resin 26 is buried in the trench 8, the fluorescent layer 27 doesnot penetrate into the trench 8. That is, the fluorescent layer 27 isformed in wafer state in which a plurality of semiconductor layers 5divided by the trench 8 are connected via the resin 26 buried in thetrench 8. Thus, the fluorescent layer 27 can be formed with a uniformthickness, and variation in chromatic characteristics can be suppressed.

The fluorescent layer with uniform thickness can be easily formed byperforming the printing process on a relatively large and flat surfacein a wafer state to form the fluorescent layer in a single process. Thisincreases the accuracy of optical design, and this is also advantageousto downsizing.

Furthermore, because the fluorescent layer 27 is formed after thesubstrate 10 is removed from above the first major surface 11 a, thesubstrate 10 does not exist between the first major surface 11 a servingas a light extraction surface and the fluorescent layer 27, which servesto increase the light extraction efficiency.

Subsequently, by cutting along the trench 8, a semiconductor lightemitting device divided into pieces is obtained. Because the substrate10 has already been removed and furthermore the resin 26 is buried inthe trench 8, dicing can be easily performed, and the productivity canbe improved. Furthermore, because the first semiconductor layer 11 andthe second semiconductor layer 12 do not exist in the trench 8, damageto these semiconductor layers at the time of dicing can be avoided. Bycutting along the trench 8 filled with the resin 26, as shown in FIG. 1,the side surface (or end surface) 11 c of the first semiconductor layer11 in the device divided into pieces is covered and protected by theresin 26.

The semiconductor light emitting device may be divided into pieces bycutting at a point surrounding one chip (semiconductor layer) 5 asindicated by dot-dashed lines in FIG. 3. Alternatively, the device maybe divided into pieces by cutting along the trench 8 surroundingmultiple chips (semiconductor layers) 5 as indicated bydouble-dot-dashed lines.

The aforementioned processes prior to dicing are each performedcollectively in wafer state, which eliminates the need ofinterconnecting and packaging for each device divided into pieces,enabling significant reduction of production cost. That is,interconnecting and packaging have already been finished in the devicedivided into pieces. Furthermore, it is easy to achieve downsizing inwhich the planar size of the individual device is close to the planarsize of the bare chip (semiconductor layer 5). Moreover, wafer-levelinspection can be performed. This can improve productivity, andconsequently cost reduction is facilitated.

Here, the substrate 10 may not be completely removed, but may be thinlyground and left on the first major surface 11 a of the firstsemiconductor layer 11 as shown in FIG. 8. The fluorescent layer 27 isprovided on the substrate 10 and opposed to the first major surface 11 avia the substrate 10.

By thinning and leaving the substrate 10, it is possible to achievehigher mechanical strength, and hence a more reliable structure than thestructure in which the substrate 10 is completely removed. Furthermore,the remaining substrate 10 can suppress warpage after divided intopieces, and it facilitates mounting on a circuit board and the like.

The material, size, shape, layout and the like of the substrate,semiconductor layer, electrode, interconnection, metal pillar,insulating film, and resin can be variously modified by those skilled inthe art.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel devices and methods describedherein may be embodied in a variety of other forms; furthermore, variousomissions, substations and changes in the form of the devices andmethods described herein may be made without departing from the spiritof the inventions. The accompanying claims and their equivalents areintended to cover such forms or modifications as would fall within thescope and spirit of the inventions.

1. A semiconductor light emitting device comprising: a semiconductorlayer having a first major surface, a second major surface formed on anopposite side to the first major surface, and a light emitting layer; afirst electrode provided on the second major surface of thesemiconductor layer; a second electrode provided on the second majorsurface of the semiconductor layer; an insulating film provided on aside of the second major surface of the semiconductor layer andincluding a first opening reaching the first electrode and a secondopening reaching the second electrode; a first interconnection providedon a surface of the insulating film on the opposite side to thesemiconductor layer and in the first opening and connected to the firstelectrode; a second interconnection provided on a surface of theinsulating film on the opposite side to the semiconductor layer and inthe second opening and connected to the second electrode; a first metalpillar provided on a surface of the first interconnection on an oppositeside to the first electrode; a second metal pillar provided on a surfaceof the second interconnection on an opposite side to the secondelectrode; a resin covering a periphery of the first metal pillar and aperiphery of the second metal pillar; and a fluorescent layer facing tothe first major surface of the semiconductor layer and including aplurality of kinds of fluorescent materials having different peakwavelengths of emission light.
 2. The device of claim 1, wherein, amongthe plurality of kinds of fluorescent materials, a fluorescent materialhaving a long peak wavelength of emission light is provided nearer tothe first major surface than a fluorescent material having a short peakwavelength of emission light.
 3. The device of claim 1, wherein thefluorescent layer includes: a first fluorescent layer provided on thefirst major surface and containing a first fluorescent material; and asecond fluorescent layer provided on the first fluorescent layer andcontaining a second fluorescent material having a shorter peakwavelength of emission light than the first fluorescent material.
 4. Thedevice of claim 3, wherein the first fluorescent material contains aSiAlON compound, the SiAlON compound exhibiting a light emission peak ata wavelength ranging from 580 to 700 nm during excitation of the firstfluorescent material caused by light with a wavelength of 250 to 500 nm.5. The device of claim 3, wherein the second fluorescent materialcontains a SiAlON compound, the SiAlON compound exhibiting a lightemission peak at a wavelength ranging from 490 to 580 nm duringexcitation of the second fluorescent material caused by light with awavelength of 250 to 500 nm.
 6. The device of claim 4, wherein thesecond fluorescent material contains a sialonSiAlON compound, thesialonSiAlON compound exhibiting a light emission peak at a wavelengthranging from 490 to 580 nm during excitation of the second fluorescentmaterial caused by light with a wavelength of 250 to 500 nm.
 7. Thedevice of claim 1, wherein the fluorescent layer includes: a transparentresin transmissive to light emitted by the light emitting layer and thefluorescent materials; and the fluorescent materials dispersed in thetransparent resin.
 8. The device of claim 1, wherein each thickness ofthe first metal pillar and the second metal pillar is thicker than athickness of a stacked body including the semiconductor layer, the firstelectrode, the second electrode, the insulating film, the firstinterconnection, and the second interconnection.
 9. The device of claim1, wherein a part of the resin covers a side surface of thesemiconductor layer.
 10. A method for manufacturing a semiconductorlight emitting device, comprising: forming a semiconductor layer on asubstrate, the semiconductor layer having a first major surface, asecond major surface formed on an opposite side of the first majorsurface, and a light emitting layer; forming a first electrode and asecond electrode on the second major surface of the semiconductor layer;forming an insulating film covering the first electrode and the secondelectrode on a side of the second major surface of the semiconductorlayer; forming a first opening and a second opening in the insulatingfilm, the first opening reaching the first electrode, the second openingreaching the second electrode; forming a first interconnection and asecond interconnection on a surface of the insulating film on anopposite side to the semiconductor layer, the first interconnectionconnected to the first electrode via the first opening, the secondinterconnection connected to the second electrode via the secondopening; forming a first metal pillar on a surface of the firstinterconnection on an opposite side to the first electrode and a secondmetal pillar on a surface of the second interconnection on an oppositeside to the second electrode; forming a resin covering a periphery ofthe first metal pillar and a periphery of the second metal pillar; andforming a fluorescent layer including a plurality of kinds offluorescent materials on the first major surface of the semiconductorlayer.
 11. The method of claim 10, wherein the forming of thefluorescent layer includes: forming a first fluorescent layer containinga first fluorescent material on the first major surface; and forming asecond fluorescent layer containing a second fluorescent material on thefirst fluorescent layer, the second fluorescent material having ashorter peak wavelength of emission light than the first fluorescentmaterial.
 12. The method of claim 10, wherein the forming of thefluorescent layer includes: supplying a transparent resin including thefluorescent materials dispersed onto the first major surface by aprinting process; and curing the transparent resin supplied onto thefirst major surface.
 13. The method of claim 10, wherein the firstinterconnection and the second interconnection are formed simultaneouslyby plating.
 14. The method of claim 10, further comprising: removing thesubstrate after the forming the first metal pillar, the second metalpillar, and the resin.
 15. The method of claim 10, further comprising:forming a trench separating the semiconductor layer into a plurality onthe substrate.
 16. The method of claim 15, further comprising: cuttingalong the trench to divide into pieces.
 17. The method of claim 15,further comprising: burying a part of the resin in the trench in theforming of the resin; and cutting the resin buried in the trench todivide into pieces.
 18. The method of claim 17, wherein the fluorescentlayer is formed on the first major surface in a wafer state in which theplurality of semiconductor layers divided by the trench are connectedvia the resin buried in the trench.
 19. The device of claim 1, wherein acontact area between the first interconnection and the first metalpillar is larger than a contact area between the first interconnectionand the first electrode.
 20. The device of claim 19, wherein a contactarea between the second interconnection and the second metal pillar islarger than a contact area between the second interconnection and thesecond electrode.